Electric discharge tube and method of manufacturing same

ABSTRACT

A vacuum-tight envelope of the tube has an aperture sealed by an indium containing material and an electrode spaced apart from the inner wall of the envelope and including a projection bonded to the sealing material.

United States Patent Vrijssen et a1.

ELECTRIC DISCHARGE TUBE AND METHOD OF MANUFACTURING SAIVIE Inventors: Gerardus Arnoldus Herman Maria Vrijssen; Jacobus Stoffels; Johannes Hendrikus Coppens, all of Eindhoven, Netherlands Assignee: U.S. Philips Corporation, New

York, NY.

Filed: May 8, 1974 Appl. No.: 468,184

Foreign Application Priority Data May 23, 1973 Netherlands 7307168 US. Cl. 174/5054; 29/25.15; 174/1705; 174/5061; 313/284; 313/482; 339/144 R Int. Cl. H01J 9/36; H011 19/50 Field of Search 174/1705, 17.08, 50.52, 174/5054, 50.61; 339/144 R; 313/477, 482, 284, 292; 29/25.15

[ Oct. 14, 1975 [56] References Cited UNITED STATES PATENTS 2,899,575 8/1959 Vincent 313/482 2,925,189 2/1960 Martin... 313/482 X 3,099,762 7/1963 Hertz 313/477 X 3,541,373 11/1970 Barr 174/5052 X 3,567,986 3/1971 Bowes et a1 313/284 X 3,582,978 6/1971 Petersen et a1. 174/5061 X 3,675,062 7/1972 Flasche 174/50.6l X 3,714,488 1/1973 Kato 313/284 X Primary Examiner.1. V. Truhe Assistant ExaminerDavid A. Tone Attorney, Agent, or FirmFrank R. Trifari; George B. Berka ABSTRACT A vacuum-tight envelope of the tube has an aperture sealed by an indium containing material and an electrode spaced apart from the inner wall of the envelope and including a projection bonded to the sealing material.

9 Claims, 4 Drawing Figures U.S. Patent Oct. 14, 1975 ELECTRIC DISCHARGE TUBE AND METHOD OF MANUFACTURING SAME The invention relates to an electric discharge tube comprising a vacuum-tight envelope, at least one electrically conductive leadthrough provided in said envelope and an electrode which is electrically conductively connected to .said leadthrough, said leadthrough consisting of an aperture provided in the envelope and sealed in a vacuum-tight manner by means of an indium-containing material.

The invention furthermore relates to a method of connecting and electrically leading-out an electrode in such a discharge tube.

Such a discharge tube is known from US. Pat. No. 3,675,062. In this Patent it is a camera tube for television in which a signal electrode provided on the face plate as a wall electrode is passed through via .an electric leadthrough provided in the said face plate. The electrically conductive material of said leadthrough consists of a plug of indium which is pressed into an aperture in the face plate and makes electric contact with the signal electrode. More than an electric contact between leadthrough and electrode is not necessary since said electrode itself readily adheres to the wall of the face plate.

However, the possibility of application of wall electrodes is restricted and in many cases it is necessary to use electrodes which are present at least partly at a distance from the wall of the envelope of the tube. Such electrodes are, for example, cathodes, control electrodes, and the gauze electrodes conventionally used in a television camera tube of the vidicon type. Each electrode involves its own problems as regards its connection in the tube and its electric leadthrough through the envelope of the tube. Known are electric discharge tubes in which the suspension and electric leadthrough of an electrode are entirely separated from each other. This is usually the case inter alia in the said gauze electrode of a television camera tube. Known are also electric discharge tubes in which the electric leadthrough provided in the envelope also ensured the suspension of the associated electrode. Such a construction is frequently used, for example, in transmitting tubes. Furthermore known are electric discharge tubes in which a combination of said methods is used. An example hereof is the conventional suspension of an electron gun from the leadthrough pins in the base of a cathoderay tube.

In the known constructions the electric leadthrough consists of a metal leadthrough which is sealed in the envelope of the tube or is secured therein by means of a vitreous material as a connection means. The electrode is secured to its leadthrough previously or afterwards. The necessary treatments which ultimately result in the finished product are not only expensive and time-consuming but often can be carried out with diffi culty only.

It is the object of the invention to provide an electric discharge tube of the type mentioned in the preamble in which both the connection and the electric leadthrough of an electrode not provided on the wall of the envelope are realized in a rapid and simple manner. For that purpose the said electric discharge tube is characterized according to the invention in that an electrode which is present internally in the tube or a part connected to said electrode is hermetically bonded to or embedded in the indium-containing material of a leadthrough associated with said electrode.

All the advantages connected with the use of a leadthrough consisting of an indium-containing material, for example, the rapid and in particular cost-saving manner in which such a leadthrough can be realized, are obtained in this case also. The influence of interference signals and cross-talk is minimized due to the particularly short electric leads between an electrode and its leadthrough. Another important advantage is that the thermal treatments of the tube which are necessary all the same, for example, the degassing of electrodes and envelopes, may also be used for bonding an electrode to its leadthrough. Degassing, connecting an electrode and manufacturing its electric leadthrough are then restricted to one operation.

In particular in the last-mentioned case it is inevitable that upon sealing the electrode the indium-containing material of the leadthrough melts entirely. When the said material solidifies again upon cooling, there is a fair chance that the electric leadthrough is no longer vacuum-tight. This can be prevented in a simple manner by providing the indium-containing material in an aperture of which at least the wall is covered with a layer of metal, preferably nickel.

Examples of indium-containing materials which satisfy the purpose underlying the invention are indium and alloys of indium and at least one of the metals platinum, gold, silver, copper, tin, lead, gallium and nickel. in the liquid phase these materials generally show the property that they readily wet other materials. This property is a necessary condition to obtain a good adhesion of an electrode to its leadthrough. Too strong a flowing of the indium-containing material over the surface of an electrode contacted therewith is not desired, however, since otherwise too little material remains in the leadthrough aperture to ensure a vacuum-tight leadthrough. In order to solve this problem both physical and chemical means are available. For example, too strong a flowing of the indium-containing material over the part of the electrode to be sealed can be counteracted by restricting the area directly available for that purpose. This can be realized in a simple manner if according to the invention an electrode comprises at least one projection for the connection which is sealed at or near the free end thereof in or to the indium-containing material of the leadthrough. It has been found that the indium-containing material then flows mainly only over the surface of the said projection.

The said problem may furthermore be solved by a suitable choice of the material of which the part of the electrode to be sealed consists. That is to say a material to which the indium-containing material readily adheres but across which it hardly flows in the liquid phase. This is met if, according to the invention, the part of the electrode to be sealed consists at least at the surface of chromium-nickel steel.

An additional possibility is that the part of the electrode to be sealed comprises near the sealing joint means which counteract too strong a flowing of the indium-containing material. This means preferably consists of a chromium layer provided on the said part to be sealed. Such a layer generally shows an oxide skin which can be wetted only to the restricted extent by the indium-containing material.

The invention will be described in greater detail with reference to a drawing, in which FIG. 1 shows, not to scale, a perspective view partially broken away of an electric discharge tube according to the invention,

FIG. 2 is an axial sectional view of a part of the tube shown in FIG. 1, and

FIGS. 3 and 4 shown other embodiments of an electrode suspension according to the invention.

The electric discharge tube shown in FIGS. 1 and 2 is a television camera tube whose envelope consists of a glass tube 1, which is sealed by a tube cap 2 and a window 3. A photosensitive layer 17 is provided on the window which is secured to the tube by means of an indium ring 16. A copper gauze electrode 4 is present within the envelope at a short distance from the window and parallel thereto. Said gauze electrode is connected between two chromium-nickel steel rings 5 and 6 which are secured together by spot welding. Three resilient lugs 7 are cut out of the ring 5 so as to be regularly divided on the circumference and, at the area where they are sealed to the indium-containing material, comprise projections 18 cooperating with the apertures 8. A layer of metal 9 is provided on the outer wall of the tube 1 so as to increase the contact area around the apertures 8. Said layer is preferably provided before the indium is pressed into the apertures 8 so that the wall of the apertures can also be lined with a thin layer of metal. In a manner similar to the gauze electrode 4, the electrode 10 is secured in the tube 1 by means of lugs 11 cut out of the wall of said electrode and the free end of which is again bonded to indium present in the apertures 12. The electrode 10 together with the wall electrode 13 which is provided with an electric leadthrough 15 forms part of a system of lenses to focus the electron rays which are produced by an electron gun which is not shown in the drawing. Said electron gun may be secured in the tube in the abovedescribed manner or in a conventional manner to the leadthrough pins 14 sealed in the tube base.

In the manufacture of an electric discharge tube according to the invention the following process is used. In the places destined for that purpose in the tube 1, apertures are provided by means of sand blasting. The walls of said apertures are covered with a thin layer of metal, preferably nickel. Possible wall electrodes as well as the enlarged contact areas 9 are provided simultaneously. The electrodes are inserted from the open ends of the tube in the axial direction and in the desired sequence and are fixed in the places of destination by means of resilient lugs snapping into the apertures. By means of projections 8 present on the free ends of the lugs, contact is made with the indium-containing material which is already present in the apertures or is to be provided therein afterwards. The said free ends of the lugs connected to the electrodes are then hermetically bonded to or in the indium-containing material of the leadthrough by degassing the tube in a vacuum space. During siad thermal treatment the indium-containing material melts in the leadthrough aperture, the layer of metal present on the wall of the aperture dissolves and adheres to the lugs connected to the electrode. After cooling the tube, a vacuum-tight leadthrough is obtained to which the electrode is hermetically bonded via the said lugs.

For a readily defined position of the electrode, at least three suspension points are necessary. However, these need not all three form an electric leadthrough. It is already sufficient for one of said suspension points to form an electric leadthrough also, while the fixation of the other points is realized by cooperation of resilient lugs connected to the electrode and cavities recessed in the wall of the tube. If desired it is possible to fill said cavities with an indium-containing material in which or to which parts connected to an electrode are bonded in a similar manner as described above. Other embodiments of an electric discharge tube according to the invention are shown in FIGS. 3 and 4. The glass tube 20 shown in FIG. 3 has a widening 21 at one end on which the window 23. which has a photosensitive layer 24 is secured by means of an indium ring 22. The gauze electrode 25 is secured in known manner between the rings 26 and 27 manufactured from coppernickel. The ring 26 bears on the shoulder 28 formed internally at the area of the widening and is sealed to an alloy of percent indium and 5 percent tin with which the aperture 29 is filled. Said indium alloy furthermore makes electric contact with a layer of nickel 30 provided on the outside on the wall of the tube for the above-mentioned reason. Besides at the area of the aperture 29, the ring 26 is furthermore secured in a similar manner in a place which is situated diametrically opposite to the aperture 29. Near said connection places the ring 26 has a chromium layer which prevents too strong a flowing of the indium during sealing the ring 26.

The embodiment according to the invention shown in FIG. 4 differs from that shown in FIG. 3 in so far that the annular shoulder 48 has been formed as a result of a local restriction of the tube 40. The gauze electrode 45 connected between the rings 46 and 47 is secured in an analogous manner and led-out electrically as described with reference to FIG. 3.

Although the invention is preferably applied to television camera tubes, it is by no means restricted to said application. The invention may very generally be used advantageously in particular in cathode-ray tubes. It will furthermore be obvious from the embodiments described that a large number of variations are possible without departing from the scope of the invention.

What is claimed is:

1. An electric discharge tube comprising a vacuumtight envelope having at least one aperture sealed by an indium-containing material to form an electrically conductive leadthrough, an electrode member arranged within said envelope, at least a portion of said member being spaced apart from the inner wall of said envelope and having a projection bonded to said indiumcontaining material.

2. An electric discharge tube as claimed in claim 1, wherein the free end of said projection is embedded in said indium-containing material.

3. An electric discharge tube as claimed in claim 1, wherein the indium-containing material includes indium or an alloy of indium and at least one metal selected from the group consisting of platinum, gold, silver, copper, tin, lead, gallium and nickel.

4. An electric discharge tube as claimed in claim 1, wherein said projection of the electrode member, at least at the surface thereof includes chromium-nickel steel.

5. An electric discharge tube as claimed in claim 1, wherein said projection, at least at the surface near the contact with said indium-containing material, comprises means which counteract too strong a flowing of the indium-containing material during its liquid phase, over the said surface.

6. An electric discharge tube as claimed in claim 5, wherein said means consist of a chromium layer provided on the said surface.

7. An electric discharge tube as claimed in claim 1, wherein at least the outer wall of the envelope is partly covered with a layer of metal making contact with the leadthrough.

8. A method of securing and electrically leadingthrough an electrode in an electric discharge tube comprising the steps of providing at least one aperture in the envelope of the tube, covering at least the wall of said aperture with a layer of metal, sealing the said aperture with a plug of indium-containing material, placing an electrode which is provided with a projection, in the envelope and bonding said projection to the said indium-containing material, heating the tube in a vacuum at such a temperature that the indium-containing material melts, alloys with the metal provided on the wall of the aperture and adheres to the projection in such manner that after cooling of the tube a vacuumtight leadthrough is obtained.

9. A method as claimed in claim 8, wherein during the bonding of said projection to said material the components of said tube are degassed. =l 

1. An electric discharge tube comprising a vacuum-tight envelope having at least one aperture sealed by an indium-containing material to form an electrically conductive leadthrough, an electrode member arranged within said envelope, at least a portion of said member being spaced apart from the inner wall of said envelope and having a projection bonded to said indiumcontaining material.
 2. An electric discharge tube as claimed in claim 1, wherein the free end of said projection is embedded in said indium-containing material.
 3. An electric discharge tube as claimed in claim 1, wherein the indium-containing material includes indium or an alloy of indium and at least one metal selected from the group consisting of platinum, gold, silver, copper, tin, lead, gallium and nickel.
 4. An electric discharge tube as claimed in claim 1, wherein said projection of the electrode member, at least at the surface thereof includes chromium-nickel steel.
 5. An electric discharge tube as claimed in claim 1, wherein said projection, at least at the surface near the contact with said indium-containing material, comprises means which counteract too strong a flowing of the indium-containing material during its liquid phase, over the said surface.
 6. An electric discharge tube as claimed in claim 5, wherein said means consist of a chromium layer provided on the said surface.
 7. An electric discharge tube as claimed in claim 1, wherein at least the outer wall of the envelope is partly covered with a layer of metal making contact with the leadthrough.
 8. A method of securing and electrically leading-through an electrode in an electric discharge tube comprising the steps of providing at least one aperture in the envelope of the tube, covering at least the wall of said aperture with a layer of metal, sealing the said aperture with a plug of indium-containing material, placing an electrode which is provided with a projection, in the envelope and bonding said projection to the said indium-containing material, heating the tube in a vacuum at such a temperature that the indium-containing material melts, alloys with the metal provided on the wall of the aperture and adheres to the projection in such manner that after coOling of the tube a vacuum-tight leadthrough is obtained.
 9. A method as claimed in claim 8, wherein during the bonding of said projection to said material the components of said tube are degassed. 